The present invention relates to water treatment systems, sometimes commonly known as water softening systems, and more particularly to a unique system comprising a water softening unit, a control system therefor, and its use in commercial/industrial settings.
Resin-type ion exchange devices have many uses, such as the softening of water. As the water to be processed is passed through the resin-filled tank, ions in the fluid to be processed, e.g. calcium, is exchanged with ions found in the resin, e.g. sodium, thereby removing objectionable ions from the water and exchanging them for less objectionable ions found in the resin. During this ion exchange process, the ability of the resin to exchange ions gradually is reduced. That is, the resin bed becomes exhausted and, thereafter, water will flow therethrough in unprocessed form.
The capacity of the ion exchange resin bed can be determined from the volume of resin used and the particular type of resin. The concentration of contaminant(s) in the water to be processed can be determined, at least on an average basis. Thus, the volume of water that can be processed by a particular water treatment unit is known. Once that capacity of water has been treated, the bed must be regenerated.
Regeneration of the ion exchange resins typically involves chemically replacing the objectionable ions from the resin with less objectionable ions, c.g. replacing calcium with sodium ions. This regeneration process requires the suspension of the treatment process, thus necessitating the water to by-pass the ion exchange resin tank. At the same time as the ion exchange resin is regenerated, the bed can be backwashed in order to remove trapped particulate matter, the resin tank can be rinsed to remove objectionable soluble materials, an application of sterilization agent to prevent bacterial growth can be accomplished, etc. All of these operations are known in the art.
In the regeneration of resin beds used to treat hard water, a variety of control modes have been employed commercially. For example, some water softening units function on a timer which necessitates regeneration at specified time intervals. This mode of operation has the disadvantage that the resin bed may have sufficient capacity remaining to continue for quite a time thereafter. Another mode of control involves monitoring the volume of water treated and provoking regeneration once a set point has been reached. Unfortunately, regeneration cycles can be triggered undesirably at just the time when demand for water is high under this mode of operation.
One overriding condsideration regardless of the mode of control employed involves exhaustion of the resin bed. If the resin bed is permitted to become completely exhausted of its capability of exchanging ions, a single regeneration cycle will not be sufficient to establish the original capacity of the bed. Instead, several regeneration cycles often will be required. Moreover, if the bed is near its exhaustion point and a high demand for water is made, present commercial systems cannot provide the capacity to soften the extra water demand without risking total exhaustion of the resin bed. Accordingly, new water treatment systems including the mode of operation thereof are in demand in this field.